Screw machines may have a number of spindles, as from one to eight. These machines perform a plurality of operations such as drilling, threading, reaming, knurling, and slotting on elongated work stock. The elongated work stock extends outside of the screw machine into work stock tubes which support the portion of the work stock which is not being operated upon by the screw machine. Only the inner end portion of the work stock is worked upon at a given time. When all of the operations have been finished on this inner end portion, the finished portion is cut off. A feed mechanism then draws the work stock further into the machine whereupon the operations are repeated on a new portion of the work stock. In a multiple spindle machine, several operating stations are provided for simultaneous work on a plurality of work stock members. In operation of a screw machine, the work stock rotates.
Conventionally, in a multiple spindle automatic screw machine, the work stock tubes are cylindrical members which are supported in angularly spaced relation by means of supporting plates. These tubes have an inner diameter capable of receiving and supporting the largest diameter work stock which the particular screw machine is capable of working upon. However, smaller diameter work stock is also receivable in such tubes, screw machines being capable of operating on work stock from a maximum to a minimum diameter. The forward end of the work stock is held by means of collet chucks. The work stock rotates at high speed in the work stock tubes. The work stock tends to rattle and bump against the inner surface of the work stock tubes thereby creating considerable noise. Additionally, wear and damage may be caused to the screw machine, work stock tubes and work stock as a consequence of this contact between the work stock and the inner surface of the work stock tubes.
The noise and wear problems, above mentioned, have been a long standing problem in connection with the operation of screw machines. Various proposals have been made in the past for minimizing this problem. For example, metal sleeves or bushings have been attached to the work stock by means of set screws. The work stock tubes have been lined with plastic stock tube liners. The work stock tubes have been wrapped externally to reduce vibration and muffle sounds. Other techniques have been proposed, as for example, in U.S. Pat. Nos. 1,786,876; 2,534,811; and 3,022,691. The various techniques used in the past have not been entirely satisfactory. For example, use of plastic stock tube liners, while effective, is very expensive. Others of the method have had the disadvantage of not reducing the noise level to the desired threshold. Still others have not functioned satisfactorily because of additional frictional drag which has been placed upon the screw machine.
Recently, it has become necessary for most machine shops using screw machines to suppress noise in some fashion as a consequence of regulations promulgated by the federal agency responsible for implementation of the Occupational Health and Hwalth Act of 1970, commonly referred to as O.S.H.A. Regulations promulgated by O.S.H.A. are being enforced. Machine shops, particularly small machine shops, have encountered difficulty in following such regulations because of the high cost involved.
In accordance with the present invention, plastic ring-like members are provided for press-fitting onto work stock. These plastic ring-like members may be supplied in various diameters with different center hole sizes for use on different sized screw machines and different sized work stock. In operation, the ring-like members are automatically removed form the work stock by abutment against screw machine structure during operation of the screw machine. Furthermore, the ring-like members are relatively inexpensive and, being fabricated of plastic, cause minimal damage if inadvertently engaged by working parts of the screw machine. Further, the ring-like members are believed to reduce the noise level of screw machines sufficiently to meet the current requirements of O.S.H.A.